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- What parts of the bundle branches are fed by the RCA?
- Posterior fascicle of the Bundle Branch.
- Which fascicle has dual blood suppply?
- Posterior Fascicle
- What will an occlusion of the LAD cause (in terms of blocks)?
-
RBBB and a Left Anterior Hemiblock (LAHB).
Remember: The posterior fascicle is spared b/c of the dual blood supply!!!! - How many seconds is the QRS in a pure LAHB?
- 0.10-0.12 seconds
- How do you diagnose an LAHB?
- Finding a Q in I and a wide or deep S in III (Q1, S3).
- In an LAHB, a slight delay in the conduction of the anterolateral and superior area of the left ventricle will cause what?
- Unopposed and late depolarization upward and leftward recognized as LAD.
- Why is Pure Posterior Hemiblock (LPHB) rare?
- b/c of the dual blood supply
- What can impair blood supply to the posterior fascicle?
- inferior wall infarction
- How does LPHB cause RAD?
- Because of the late and unopposed depolarization force towards the right.
- How can you tell that there is a posterior block?
- Look for deep unusually wide S in lead I and Q in lead III (S1, Q3).
- PRI >0.20 but consistent.
- 1 Degree AVB
- PRI >0.20 and getting longer until it drops a QRS.
- 2 Degree Type I (Wenckebach)
- QRS <0.12 with no PRI
- 3 Degree Complete Heart Block
- QRS <0.10 with atrial rate twice ventricular rate
- 2 Degree Type II AVB
- QRS >0.12 with atrial rate twice ventricular rate
- 3 Degree Complete Heart Block
- SSS
- Group of dysrhythmias that share alternating fast and slow rhythms SB, ST, Sinus Block, and failure of escape pacemakers)
- Abrupt sinus arrest associated with loss of consciousness usually describes what dysrhythmia?
- SSS
- Brady-Tachy Syndrome
- Intermittent episodes of SVT, A-Fib, or A-flutter, with sinus brady seen in pts with SSS
- What is a cause of Brady-Tachy Syndrome?
- Hypersensitive Carotid Sinus - shaving or wearing a necktie too tight around Carotid Sinus area.
- This is said to be the "Wastebasket" of dysrhythmias.
- SSS
- What causes SSS?
- SA node dysfunction associated with unresponsive supraventricular automaticity foci.
- Ectopy/Ectopic Rhythms
- Abnormal rhythms that arise from elsewhere other thanthe sinus node.
- What are the two ways that ectopic beats can arise on the cellular level?
-
-Enhanced Automaticity (other pacemakers take over - disorder in impulse formation)
-Reentry (disorder in impulse transmission)